This invention relates to an improvement in the method for electrochemical machining.
With the mechanical machining technique, it is difficult to machine a sparingly malleable material such as of heatresistant alloy faithfully to a desired complicated shape. Thus, there is adopted the electrochemical machining technique. By the conventional electrochemical machining method, desired machining has been effected by approaching the cathode to the work within the electrolyte to the extent of interposing therebetween a gap of 0.02 to 0.7 mm and causing a flow of direct current of high current density of the order of from 30 to 300 A/cm.sup.2 to pass between the work blank and the cathode. When the electrolysis is effected by use of direct current within an unmoving electrolyte, however, the ions, gases, etc. generated in consequence of the electrolyzing action stagnate in the gap between the work blank and the cathode to interfere with the effective flow of electric current at high current density and consequently cause local buildup of heat in the electrolyte. To preclude this phenomenon of stagnation and its attendant hindrances, the electrolyte is forced by some means or other to flow at a high rate of not less than 10 m/second during the machining or the cathode is provided with an injection nozzle adapted to induce a local flow of the electrolyte when necessary.
The forced flow of the electrolyte, however, necessitates incorporation of an extra device for generating flow. Further, the movement of the electrolyte tends to result in degradation of the machining accuracy. In the case of providing the cathode with the injection nozzle, the cathode is inevitably limited in its thickness so that an attempt to use, as the cathode a thin wire less than 0.5 mm in diameter turns out to be futile.
To avoid the various disadvantages described above. I proposed a method for effecting the electrochemical machining by use of a pulsed electric current having a pulse width of from 0.01 to 10 ms and a duty factor of not more than 0.5 (U.S. Patent Application Ser. No. 602,135), filed Aug. 5, 1975, instead of using the direct current used in the conventional method for electrochemical machining. Owing to the use of such a pulsed electric currennt, gas is formed intermittently by electrochemical action and the electrolyte in the machining zone between the work blank and the cathode is consequently agitated. Since the electrolyte in the gap is in an agitated state, desired electrochemical machining of a sparingly malleable material can be effectively carried out with high accuracy without necessity of a forced flow of the electrolyte.
In the U.S. Patent Application mentioned above, the electrochemical machining disclosed is limited to boring of fine perforations, removabl of burrs occurring along the periphery of said perforations and rectilinear cutting,
Recently, a method for electric discharge machining has been developed. Unlike the conventional method for electrochemical machining, this method dispenses with the forced flow of the electrolyte. Nevertheless, it consumes the electrode in the course of machining and, therefore, necessitates frequent supply of a fresh electrode. For this reason, the electrode to be used in this method is limited to that of a straight wire. According to this method it is difficult to machine the work blank to a complicated shape by use of a curved electrode.
An object of the present invention is to provide a method for the electrochemical machining which, by using as the electrode a thin wire deviating from a recti-linear shape, permits the work blank to be machined to a desired complicated shape with high accuracy.